Reticle SMIF pod (RSP) is used for storing mask in a small housing with ultimate clean. However, for storing EUV mask or EUV reticle, requirement of clean is extremely crucial than conventional reticle SMIF pod and dual pod is therefore provided. As shown in FIG. 1, the dual pod 10 includes two pods, in which one is an outer pod 14 compatible to original reticle SMIF pod, and the other one is an inner pod 12 or EUV pod for storing EUV mask. The inner pod 12, just a little larger than the EUV mask, can be placed into the outer pod 14. Although the dual pod is better for storing EUV mask, however, in order to facilitate with dual pod, all equipments in a semiconductor industry will be designed again. That would induce much more cost.
Now, in semiconductor industry, some companies may need dual pod, but some other companies may not need dual pod. For the two kinds of pods, a sorter is used as an interface for operating the two kinds of pods. For example, if a vendor provides an EUV mask stored inside the dual pod while only conventional RSP is available in the manufacture company, or vice versa, the sorter can be used to place the EUV mask from the dual pod into the RSP, or vice versa.
A system 20 for processing mask, such as inspecting the mask or illuminating the mask in lithography process, with sorter is shown in FIG. 2, wherein the system 20 includes a sorter 22, a transfer chamber 32, and a processing chamber 36. The sorter 22, in air condition, includes a dual pod port 24 for loading/unloading the dual pod, a RSP port 26 for loading/unloading the RSP, an opener chamber 28 for opening inner pod of the dual pod, and a chamber that the dual pod port 24, RSP port 26, and opener chamber 28 connecting thereto. Sorter 22 is used for EUV mask transferred from reticle SMIF pod to dual pod or vice versa. If an EUV mask stored in a dual pod and will be transferred into RSP, a solid curve line indicates the EUV mask transferring procedure, or vice versa.
A load/lock 30 connecting to the chamber of the sorter 22 will provide an interface for reticle between the air condition and class 1 vacuum condition, or air condition and class 1 vacuum condition for ebeam inspection. A dash line in FIG. 2 across the load/lock 30 denotes the interface between air and vacuum. A transfer chamber 32, with an opener chamber 34 connecting thereto, connecting to the load/lock 30 for receiving EUV mask or inner pod of the dual pod before the EUV mask enters the processing chamber 36. Transfer chamber 32 is used for transferring EUV mask from reticle SMIF pod or dual pod into processing tool, such as lithography or inspection tool.
For EUV mask stored in reticle SMIF pod, a port for reticle SMIF pod is ready to load, and directly transferred into E-chuck via transfer chamber for litho use. As shown in FIG. 2, for an EUV mask stored inside the RSP, the RSP is loaded to the RSP port 26 and the EUV mask is then took off through the load/lock 30 into the processing chamber 36 directly. Such a procedure can be referred to the dash curve line in FIG. 2.
For EUV mask stored in dual pod, EUV mask is passed into opener chamber in the transfer chamber to open the inner pod. As shown in FIG. 2, for an EUV mask stored in the dual pod, the dual pod will be loaded on the dual port 24 and the inner pod will be loaded through the load/lock 30 to the opener chamber 34 connecting to the transfer chamber 32. Then, the inner pod is opened and the EUV mask inside the inner pod is then took off, and transferred to the processing chamber 36. This procedure can be referred to the dot-dash line in FIG. 2.
EUV mask, in lithography use, always faces down; however, the EUV mask has to be flipped for inspection purpose. Hence, a flipper should be included in the chamber of the sorter 22. Further, the EUV mask has a square outline, and has to be turned by angles. Therefore, a turn table is also included in the chamber of the sorter 22.
Although the system 20 as shown in FIG. 2 provides a good interface for both dual pod and RSP, it occupied too large footprint. Moreover, the system 20 is also too complex that will increase cost for foundry. Therefore, a new system is needed for small footprint with simple mechanism.